Projection optical system and projection type display device

ABSTRACT

A projection optical system is constituted by, in order from the reduction side, a first optical system for forming an image displayed by image display elements as an intermediate image, a first optical path bending means that bends an optical path with a reflective surface, and a second optical system for forming the intermediate image on a magnification side conjugate plane. The second optical system is constituted by, in order from the reduction side, a first lens group having a positive refractive power, a second optical path bending means that bends an optical path with a reflective surface, and a second lens group having a positive refractive power. Conditional Formulae (1) and (2) below are satisfied. 
       10.0&lt; TL 1/| f |&lt;50.0   (1)
 
       4.0&lt; TL 21/| f |&lt;30.0   (2).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 15/044,531 filed on Feb. 16, 2016, which claims priority under 35U.S.C. § 119 to Japanese Patent Application No. 2015-035085 filed onFeb. 25, 2015. The above application is hereby expressly incorporated byreference, in its entirety, into the present application.

BACKGROUND

The present disclosure is related to a projection optical system and aprojection type display device. Particularly, the present disclosure isrelated to a projection optical system which is favorably suited for usein a projection type display device having light valves such as liquidcrystal display elements or DMD's (Digital Micromirror Devices®), and aprojection type display device that employs this projection opticalsystem.

Recently, projection type display devices (also referred to as“projectors”) which are equipped with light valves such as liquidcrystal display elements and DMD's (Digital Micromirror Devices®) are inwide use, and the performance thereof is increasing. Particularly,accompanying the improved performance of recent light valves, there isgreat demand for the resolution of projection optical systems to beimproved as well.

In addition, there is increasing demand for projection optical systemshaving higher performance and wider angles of view to be mounted inprojection type display devices, taking increases in the degree offreedom in setting distances to screens and installation propertieswithin interior spaces into consideration.

Projection optical systems that form an intermediate image with a firstoptical system constituted by a plurality of lenses, then performrefocusing operations with a second optical system also constituted by aplurality of lenses have been proposed, in order to meet these demands(refer to International Patent Publication No. 09/107553 and JapaneseUnexamined Patent Publication No. 2006-330410).

In a projection optical system constituted by an ordinary optical systemthat does not form an intermediate image, if a widening of the angle ofview is achieved by shortening the focal length thereof, the lensestoward the magnification side will become excessively large. Incontrast, a projection optical system that forms an intermediate imageas described above is capable of shortening the back focus of the secondoptical system while decreasing the diameters of lenses of the secondoptical system toward the magnification side, and is favorably suited toincreasing the angle of view by shortening the focal length thereof.

SUMMARY

However, International Patent Publication No. 09/107553 discloses anoptical system in which the second optical system is a fish eye lens,which results in distortion remaining to a great degree in a final imagesurface. Therefore, this optical system is not favorably suited for useas a general projection optical system. In addition, aberrations arecorrected independently by a first optical system and a second opticalsystem with an intermediate image at the boundary therebetween in theprojection optical system of Japanese Unexamined Patent Publication No.2006-330410. Therefore, a widening of the angle of view cannot beachieved to a degree which is becoming required recently. Further,because the optical systems disclosed in both International PatentPublication No. 09/107553 and Japanese Unexamined Patent Publication No.2006-330410 form an intermediate image, the total lengths of theseoptical systems will increase as a matter of course.

The present disclosure has been developed in view of the foregoingcircumstances. The present disclosure provides a projection opticalsystem that forms an intermediate image having high projectionperformance with a wide angle of view, in which various aberrations arefavorably corrected and that achieves miniaturization. The presentdisclosure also provides a projection type display device equipped withthis projection optical system.

The projection optical system of the present disclosure is a projectionoptical system that projects images displayed by image display elementsprovided on a reduction side conjugate plane onto a magnification sideconjugate plane as a magnified image, consisting of, in order from thereduction side to the magnification side:

a first optical system constituted by a plurality of lenses that formsthe image displayed by the image display elements as an intermediateimage;

a first optical path bending means for bending an optical path with areflective surface; and

a second optical system constituted by a plurality of lenses thatfocuses the intermediate image on the magnification side conjugateplane;

the second optical system consisting of, in order from the reductionside to the magnification side, a first lens group having a positiverefractive power, a second optical path bending means for bending anoptical path with a reflective surface, and a second lens group having apositive refractive power; and

Conditional Formulae (1) and (2) below being satisfied:

10.0<TL1/|f|<50.0   (1)

4.0<TL21/|f|<30.0   (2)

wherein TL1 is the distance along the optical axis from the surface mosttoward the reduction side to the surface most toward the magnificationside within the first optical system, TL21 is the distance along theoptical axis from the surface most toward the reduction side to thesurface most toward the magnification side within the first lens group,and f is the focal length of the entire projection optical system.

In the projection optical system of the present disclosure, it ispreferable for Conditional Formulae (1-1) and (2-1) below to besatisfied.

15.0<TL1/|f|<40.0   (1-1)

6.0<TL21/|f|<20.0   (2-1).

In addition, it is preferable for Conditional Formulae (3) and (4) belowto be satisfied. Note that it is more preferable for ConditionalFormulae (3-1) and (4-1) below to be satisfied.

8.0<D12/|f|<30.0   (3)

10.0<D12/|f|<25.0   (3-1)

5.0<D212/|f|<20.0   (4)

6.0<D212/|f|<15.0   (4-1)

wherein D12 is the distance along the optical axis between the firstoptical system and the second optical system, D212 is the distance alongthe optical axis between the first lens group and the second lens group,and f is the focal length of the entire projection optical system.

In addition, it is preferable for Conditional Formula (5) below to besatisfied. Note that it is more preferable for Conditional Formula (5-1)below to be satisfied.

1.50<f2/|f|<2.80   (5)

1.52<f2/|f|<2.20   (5-1)

wherein f2 is the focal length of the second optical system, and f isthe focal length of the entire projection optical system.

In addition, it is preferable for Conditional Formula (6) below to besatisfied. Note that it is more preferable for Conditional Formula (6-1)below to be satisfied.

8.20<Imφ·f2/f ²<20.00   (6)

8.3<Imφ·f2/f ²<16.00   (6-1)

wherein Imφ is the effective image diameter at the reduction side, f2 isthe focal length of the second optical system, and f is the focal lengthof the entire projection optical system.

In addition, it is preferable for Conditional Formula (7) below to besatisfied. Note that it is more preferable for Conditional Formula (7-1)below to be satisfied.

0.020<enP/TL2<0.160   (7)

0.050<enP/TL2<0.145   (7-1)

wherein enP is the distance along the optical axis from the surface mosttoward the magnification side in the second optical system to theposition of an entrance pupil in the case that the magnification side isa light entry side, and TL2 is the distance along the optical axis fromthe surface most toward the reduction side in the second optical systemto the surface most toward the magnification side in the second opticalsystem.

In addition, it is preferable for Conditional Formula (8) below to besatisfied. Note that it is more preferable for Conditional Formula (8-1)below to be satisfied.

0.125<Imφ/TL2<0.240   (8)

0.130<Imφ/TL2<0.200   (8-1)

wherein Imφ is the effective image diameter at the reduction side, andTL2 is the distance along the optical axis from the surface most towardthe reduction side in the second optical system to the surface mosttoward the magnification side in the second optical system.

In addition, it is preferable for Conditional Formula (9) below to besatisfied. Note that it is more preferable for Conditional Formula (9-1)to be satisfied.

0.30<f22/f21<2.00   (9)

0.40<f22/f21<1.70   (9-1)

wherein f21 is the focal length of the first lens group, and f22 is thefocal length of the second lens group.

In addition, it is preferable for Conditional Formula (10) to besatisfied. Note that it is more preferable for Conditional Formula(10-1) to be satisfied.

4.0<Bf/|f|  (10)

5.0<Bf/|f|<20.0   (10-1)

wherein Bf is the back focus (air converted distance) of the entireprojection optical system, and f is the focal length of the entireprojection optical system.

In addition, it is preferable for a principal light ray at the maximumangle of view and the optical axis of the second optical system tointersect between the first lens group and the second lens group.

In addition, the intermediate image may be configured such that theperipheral portion has more field curvature toward the first opticalsystem than the portion thereof at the center of the optical axis.

In addition, it is preferable for the first optical path bending meansand/or the second optical path bending means to be a mirror.

In addition, it is preferable for the first optical path bending meansand/or the second optical path bending means to be provided atorientations that bend optical paths at angles of 90 degrees.

In addition, it is preferable for images which are displayed by imagedisplay elements to be projected as enlarged images which are inverted180 degrees.

A projection type display device of the present disclosure comprises alight source, light valves into which light from the light sourceenters, and a projection optical system of the present disclosure as aprojection optical system that projects an optical image formed by lightwhich is optically modulated by the light valves.

Note that the “magnification side” refers to the side toward whichoptical images are projected (the side toward a screen). For the sake ofconvenience, the side toward the screen will be referred to as themagnification side even in cases that optical images are reduced andprojected. Meanwhile, the “reduction side” refers to a side toward anoriginal image display region (the side toward a light valve). For thesake of convenience, the side toward the light valve will be referred toas the reduction side even in cases that images are reduced andprojected.

In addition, the expression “consisting of” means that the projectionoptical system may include: lenses without any practical refractivepower; and optical elements other than lenses such as stops, masks, acover glass, and filters, in addition to the constituent elements whichare listed above.

In addition, a “lens group” is not necessarily constituted by aplurality of lenses, and may be constituted by a single lens.

In addition, with respect to the “back focus”, the magnification sideand the reduction side are respectively considered as corresponding tothe object side and the image side of a common imaging lens, and themagnification side and the reduction side are respectively designated asthe front side and the back side of the optical system.

In addition, “Imφ” can be obtained from the specification of theprojection optical system, the specification of the apparatus on whichthe projection optical system is mounted, for example.

In addition, the surface shapes and the signs of the refractive indicesof the lenses are those which are considered in the paraxial region incases that aspherical surfaces are included.

The projection optical system of the present disclosure is a projectionoptical system that projects images displayed by image display elementsprovided on a reduction side conjugate plane onto a magnification sideconjugate plane as a magnified image, consisting of, in order from thereduction side to the magnification side: a first optical systemconstituted by a plurality of lenses that forms the image displayed bythe image display elements as an intermediate image; a first opticalpath bending means for bending an optical path with a reflectivesurface; and a second optical system constituted by a plurality oflenses that focuses the intermediate image on the magnification sideconjugate plane; the second optical system consisting of, in order fromthe reduction side to the magnification side, a first lens group havinga positive refractive power, a second optical path bending means forbending an optical path with a reflective surface, and a second lensgroup having a positive refractive power; and Conditional Formulae (1)and (2) below being satisfied:

10.0<TL1/|f|<50.0   (1)

4.0<TL21/|f|<30.0   (2)

Therefore, it becomes possible to realize a projection optical systemhaving high projection performance with a wide angle of view, in whichvarious aberrations are favorably corrected and that achievesminiaturization.

In addition, the projection type display device of the presentdisclosure is equipped with the projection optical system of the presentdisclosure. Therefore, the apparatus can be miniaturized, and imageshaving high image quality can be projected at a wide angle of view.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional diagram that illustrates the configuration of aprojection optical system according to an embodiment of the presentdisclosure (common with Example 1).

FIG. 2 is a sectional diagram that illustrates the configuration of aprojection optical system according to Example 2 of the presentdisclosure.

FIG. 3 is a sectional diagram that illustrates the configuration of aprojection optical system according to Example 3 of the presentdisclosure.

FIG. 4 is a sectional diagram that illustrates the configuration of aprojection optical system according to Example 4 of the presentdisclosure.

FIG. 5 is a sectional diagram that illustrates the configuration of aprojection optical system according to Example 5 of the presentdisclosure.

FIG. 6 is a sectional diagram that illustrates the configuration of aprojection optical system according to Example 6 of the presentdisclosure.

FIG. 7 is a sectional diagram that illustrates the configuration of aprojection optical system according to Example 7 of the presentdisclosure.

FIG. 8 is a collection of diagrams that illustrate aberrations of theprojection optical system of Example 1.

FIG. 9 is a collection of diagrams that illustrate aberrations of theprojection optical system of Example 2.

FIG. 10 is a collection of diagrams that illustrate aberrations of theprojection optical system of Example 3.

FIG. 11 is a collection of diagrams that illustrate aberrations of theprojection optical system of Example 4.

FIG. 12 is a collection of diagrams that illustrate aberrations of theprojection optical system of Example 5.

FIG. 13 is a collection of diagrams that illustrate aberrations of theprojection optical system of Example 6.

FIG. 14 is a collection of diagrams that illustrate aberrations of theprojection optical system of Example 7.

FIG. 15 is a diagram that schematically illustrates the configuration ofa projection type display device according to an embodiment of thepresent disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. FIG. 1 is asectional diagram that illustrates the configuration of a projectionoptical system according to an embodiment of the present disclosure. Theexample illustrated in FIG. 1 corresponds to a projection optical systemof Example 1 to be described later. In FIG. 1, the side of an imagedisplay surface Sim is the reduction side, and the side of a final lensL32 of the second optical system G2 is the magnification side. Theaperture stop St illustrated in FIG. 1 does not necessarily representthe size or shape thereof, but the position thereof along an opticalaxis Z. In addition, FIG. 1 also shows an axial light beam wa and alight beam wb at a maximum angle of view.

This projection optical system may be mounted in a projection typedisplay device and utilized to project image information displayed onlight valves onto a screen. In FIG. 1, a case in which the projectionoptical system is mounted in a projection type display device isassumed, and an optical member PP that assumes filters, prisms, and thelike which are employed in a color combining section or an illuminatinglight separating section as well as the image display surface Sim of thelight valves positioned at the surface of the optical member PP towardthe reduction side are also illustrated. In the projection type displaydevice, light beams onto which image information is imparted by theimage display surface Sim enter the projection optical system via theoptical member PP, and are projected onto a screen (not shown) by theprojection optical system.

As illustrated in FIG. 1, the projection optical system consists of, inorder from the reduction side to the magnification side: a first opticalsystem G1 constituted by a plurality of lenses that forms the imagedisplayed by the image display elements as an intermediate image; afirst optical path bending means R1 for bending an optical path with areflective surface, and a second optical system G2 constituted by aplurality of lenses that focuses the intermediate image on amagnification side conjugate plane.

The second optical system G2 consists of, in order from the reductionside to the magnification side, a first lens group G21 having a positiverefractive power, a second optical path bending means R2 for bending anoptical path with a reflective surface, and a second lens group G22having a positive refractive power.

In an ordinary projection optical system constituted only by an opticalsystem that does not form an intermediate image, if a widening of theangle of view is achieved by shortening the focal length thereof, thelenses toward the magnification side will become excessively large. Incontrast, the projection optical system of the present embodiment thatforms an intermediate image is capable of shortening the back focus ofthe second optical system G2 while decreasing the diameters of lenses ofthe second optical system G2 toward the magnification side, and isfavorably suited to increasing the angle of view by shortening the focallength thereof.

By providing the optical path bending means in intermediate positionswithin the projection optical system in this manner, the optical pathbending means can be miniaturized compared to a case in which an opticalpath bending means is provided at the magnification side of a projectionoptical system. In addition, by providing two optical path bending meanswithin the projection optical system, miniaturization of the projectionoptical system as a whole and control of the projection direction isfacilitated.

Note that in the projection optical system of the present embodiment,the reduction side is configured to be telecentric. Here, the expression“the reduction side is telecentric” means that an angular line thatbisects the cross section of a light beam focused at an arbitrary pointon the image display surface Sim, which is the reduction conjugateplane, between the maximum ray of light at the upper side and themaximum ray of light at the lower side thereof is close to beingparallel with the optical axis Z. The expression “the reduction side istelecentric” is not limited to cases in which the reduction side iscompletely telecentric, that is, cases in which the bisecting angularline is completely parallel to the optical axis, but also refers tocases in which a certain degree of error is present. Here, the certaindegree of error refers to a range of inclination between the bisectingangular line and the optical axis Z of ±3°.

In addition, the projection optical system is configured such thatConditional Formulae (1) and (2) below are satisfied. ConditionalFormula (1) defines the ratio between the lens length of the firstoptical system G1 and the focal length of the entire projection opticalsystem. By Conditional Formula (1) being satisfied, the relaymagnification rate of the first optical system can be favorablymaintained, a widening of the angle of view can be achieved, variousaberrations can be corrected, and miniaturization can be achieved. Byconfiguring the projection optical system such that the value of TL1/|f|is not greater than or equal to the upper limit defined in ConditionalFormula (1), the lens length of the first optical system G1 can beprevented from becoming excessively long, and miniaturization can beachieved. By configuring the projection optical system such that thevalue of TL1/|f| is not less than or equal to the lower limit defined inConditional Formula (1), the relay magnification rate of the firstoptical system G1 can be prevented from becoming excessively great. As aresult, the diameters of the lenses within the second optical system G2can be prevented from increasing. In addition, correction of distortionand field curvature by the second optical system G2 will be facilitated.Further, the light emission angles from the first optical system G1 tothe second optical system G2 can be prevented from becoming excessivelylarge in the dispersing direction. Therefore, securing space for bendingoptical paths is facilitated. Conditional Formula (2) defines the ratiobetween the lens length of the first lens group G21 and the focal lengthof the entire projection optical system. By Conditional Formula (2)being satisfied, an appropriate distance can be maintained between thefirst optical path bending means R1 and the second optical path bendingmeans R2, while achieving miniaturization. By configuring the projectionoptical system such that the value of TL21/|f| is not greater than orequal to the upper limit defined in Conditional Formula (2), the lenslength of the first lens group G21 can be prevented from becomingexcessively long, and miniaturization can be achieved. By configuringthe projection optical system such that the value of TL21/|f| is notless than or equal to the lower limit defined in Conditional Formula(2), the distance between the first optical path bending means R1 andthe second optical path bending means R2 can be prevented from becomingexcessively small. As a result, the possibility of interference can beeliminated. Note that more favorable properties can be obtained ifConditional Formula (1-1) and/or Conditional Formula (2-1) below aresatisfied.

10.0<TL1/|f|<50.0   (1)

15.0<TL1/|f|<40.0   (1-1)

4.0<TL21/|f|<30.0   (2)

6.0<TL21/|f|<20.0   (2-1)

wherein TL1 is the distance along the optical axis from the surface mosttoward the reduction side to the surface most toward the magnificationside within the first optical system, TL21 is the distance along theoptical axis from the surface most toward the reduction side to thesurface most toward the magnification side within the first lens group,and f is the focal length of the entire projection optical system.

In the projection optical system of the present embodiment, it ispreferable for Conditional Formulae (3) and (4) below to be satisfied.Conditional Formula (3) defines the ratio between the distance betweenthe first optical system G1 and the second optical system G2, and thefocal length of the entire projection optical system. By configuring theprojection optical system such that the value of D12/|f| is not greaterthan or equal to the upper limit defined in Conditional Formula (3), thedistance between the first optical system G1 and the second opticalsystem G2 can be prevented from becoming excessively great, andminiaturization can be achieved. By configuring the projection opticalsystem such that the value of D12/|f| is not less than or equal to thelower limit defined in Conditional Formula (3), a sufficient amount ofspace for placing the first optical path bending means R1 can besecured. As a result, the probability of foreign matter, damage, etc. onthe first optical path bending means R1 being projected onto a screencan be reduced. Conditional Formula (4) defines the ratio between thedistance between the first lens group G21 and the second lens group G22and the focal length of the entire projection system. By configuring theprojection optical system such that the value of D212/|f| is not greaterthan or equal to the upper limit defined in Conditional Formula (4), thedistance between the first lens group G21 and the second lens group G22can be prevented from becoming excessively great, and miniaturizationcan be achieved. By configuring the projection optical system such thatthe value of D212/|f| is not less than or equal to the lower limitdefined in Conditional Formula (4), a sufficient amount of space forplacing the second optical path bending means R2 can be secured. Notethat more favorable properties can be obtained if Conditional Formula(3-1) and/or Conditional Formula (4-1) below are satisfied.

8.0<D12/|f|<30.0   (3)

10.0<D12/|f|<25.0   (3-1)

5.0<D212/|f|<20.0   (4)

6.0<D212/|f|<15.0   (4-1)

wherein D12 is the distance along the optical axis between the firstoptical system and the second optical system, D212 is the distance alongthe optical axis between the first lens group and the second lens group,and f is the focal length of the entire projection optical system.

In addition, it is preferable for Conditional Formula (5) below to besatisfied. Conditional Formula (5) defines the ratio between the focallength of the second optical system G2 and the focal length of theentire projection optical system. This ratio corresponds to the relaymagnification rate of the first optical system G1 that forms theintermediate image. By Conditional Formula (5) being satisfied, a relaymagnification rate can be appropriately set in order to achieve a wideangle of view by the relay method. As a result, it becomes possible toachieve a widening of the angle of view, while appropriately correctingvarious aberrations which become problems when widening the angle ofview. By configuring the projection optical system such that the valueof f2/|f| is not greater than or equal to the upper limit defined inConditional Formula (5), the relay magnification rate, and therefore thesize of the intermediate image, can be prevented from increasing. As aresult, increases in the diameters of the lenses within the secondoptical system G2 can be prevented. In addition, correction ofdistortion and field curvature in the second optical system G2 can befacilitated. The FNo. required of the second optical system G2 is theFNo. of the entire projection optical system multiplied by the relaymagnification rate. By configuring the projection optical system suchthat the value of f2/|f| is not less than or equal to the lower limitdefined in Conditional Formula (5), the F value (FNo.) required of thesecond optical system G2 can be prevented from becoming excessivelysmall. As a result, correction of aberrations (particularly sphericalaberration and astigmatism) corresponding to a widened angle of view anda fast lens having a small F value is facilitated. Note that morefavorable properties can be obtained if Conditional Formula (5-1) belowis satisfied.

1.50<f2/|f|<2.80   (5)

1.52<f2/|f|<2.20   (5-1)

wherein f2 is the focal length of the second optical system, and f isthe focal length of the entire projection optical system.

In addition, it is preferable for Conditional Formula (6) below to besatisfied. Conditional Formula (6) defines the relationship among theeffective image diameter at the reduction side, the focal length of thesecond optical system G2, and the focal length of the entire projectionoptical system. By configuring the projection optical system such thatthe value of Imφ·f2/f² is not greater than or equal to the upper limitdefined in Conditional Formula (6), the effective image diameter can beprevented from becoming excessively great with respect to the focallength of the entire projection optical system, and the power of thesecond optical system G2 can be prevented from becoming excessively weakwith respect to the focal length of the entire projection opticalsystem. As a result, the diameters of the lenses of the second opticalsystem G2 can be decreased, and the entire projection optical system canbe miniaturized. By configuring the projection optical system such thatthe value of Imφ·f2/f² is not less than or equal to the lower limitdefined in Conditional Formula (6), the effective image diameter can beprevented from becoming excessively small with respect to the focallength of the entire projection optical system, and the power of thesecond optical system G2 can be prevented from becoming excessivelystrong with respect to the focal length of the entire projection opticalsystem. As a result, the requirements for the second optical system G2to correct aberrations (particularly spherical aberration andastigmatism) are lessened, and realizing high performance isfacilitated. Note that more favorable properties can be obtained ifConditional Formula (6-1) below is satisfied.

8.20<Imφ·f2/f ²<20.00   (6)

8.3<Imφ·f2/f ²<16.00   (6-1)

wherein Imφ is the effective image diameter at the reduction side, f2 isthe focal length of the second optical system, and f is the focal lengthof the entire projection optical system.

In addition, it is preferable for Conditional Formula (7) below to besatisfied. Conditional Formula (7) defines the ratio between thedistance along the optical axis from the surface most toward themagnification side in the second optical system G2 to the position of anentrance pupil in the case that the magnification side is a light entryside and the total length of the second optical system G2. In anordinary optical system that does not form an intermediate image, it isnecessary to secure a long back focus. However, it is not necessary tosecure a long back focus for the second optical system G2 in the presentembodiment because an intermediate image is formed. Therefore, it ispossible to move the position of the entrance pupil more toward themagnification side compared to an ordinary optical system that does notform an intermediate image, and a widening of the angle of view can beachieved while decreasing the diameter of the lens most toward themagnification side within the second optical system G2. ConditionalFormula (7) defines the ratio that enables this state to be achieved. Byconfiguring the projection optical system such that the value of enP/TL2is not greater than or equal to the upper limit defined in ConditionalFormula (7), the position of the entrance pupil can be moved more towardthe magnification side, and securing a desired angle of view isfacilitated. By configuring the projection optical system such that thevalue of enP/TL2 is not less than or equal to the lower limit defined inConditional Formula (7), the total length of the second optical systemG2 can be prevented from becoming excessively long, while suppressing anincrease in the diameter of the lens most toward the magnification sidewithin the second optical system G2. Note that more favorable propertiescan be obtained if Conditional Formula (7-1) below is satisfied.

0.020<enP/TL2<0.160   (7)

0.050<enP/TL2<0.145   (7-1)

wherein enP is the distance along the optical axis from the surface mosttoward the magnification side in the second optical system to theposition of an entrance pupil in the case that the magnification side isa light entry side, and TL2 is the distance along the optical axis fromthe surface most toward the reduction side in the second optical system.

In addition, it is preferable for Conditional Formula (8) below to besatisfied. Conditional Formula (8) defines the ratio between theeffective image diameter at the reduction side and the total length ofthe second optical system G2. By configuring the projection opticalsystem such that the value of Imφ/TL2 is not greater than or equal tothe upper limit defined in Conditional Formula (8), increases in thesensitivity to error of individual lenses within the second opticalsystem G2 due to excessive miniaturization can be suppressed, andproductivity can be maintained. By configuring the projection opticalsystem such that the value of Imφ/TL2 is not less than or equal to thelower limit defined in Conditional Formula (8), a desired effectiveimage diameter can be obtained, while the total length of the secondoptical system G2 can be prevented from becoming excessively great. Notethat more favorable properties can be obtained if Conditional Formula(8-1) below is satisfied.

0.125<Imφ/TL2<0.240   (8)

0.130<Imφ/TL2<0.200   (8-1)

wherein Imφ is the effective image diameter at the reduction side, andTL2 is the distance along the optical axis from the surface most towardthe reduction side in the second optical system.

In addition, it is preferable for Conditional Formula (9) below to besatisfied. Conditional Formula (9) defines the ratio between the focallengths of the first lens group G21 and the second lens group G22 withinthe second optical system G2. By configuring the projection opticalsystem such that the value of f22/f21 is not greater than or equal tothe upper limit defined in Conditional Formula (9), the power of thefirst lens group G21 will be prevented from becoming excessively strongwith respect to that of the second lens group G22. As a result, theincident angles of light that enters the first optical system G1 can beprevented from becoming excessively great, and correcting aberrations inthe first optical system G1 will be facilitated. By configuring theprojection optical system such that the value of f22/f21 is not lessthan or equal to the lower limit defined in Conditional Formula (9), thepower of the second lens group G22 will be prevented from becomingexcessively strong with respect to that of the first lens group G21. Asa result, correcting distortion in the second lens group G22 will befacilitated. Note that more favorable properties can be obtained ifConditional Formula (9-1) below is satisfied.

0.30<f22/f21<2.00   (9)

0.40<f22/f21<1.70   (9-1)

wherein f21 is the focal length of the first lens group, and f22 is thefocal length of the second lens group.

In addition, it is preferable for Conditional Formula (10) below to besatisfied. Conditional Formula (10) defines the back focus of the entireprojection optical system, and sets a sufficient back focus necessaryfor a space to provide a color combining prism and the like at thereduction side of the entire projection optical system. By configuringthe projection optical system such that the value of Bf/|f| is not lessthan or equal to the lower limit defined in Conditional Formula (10),the back focus can be prevented from becoming excessively short. As aresult, providing a color combining prism and the like is facilitated.Note that more favorable properties can be obtained if ConditionalFormula (10-1) below is satisfied. By configuring the projection opticalsystem such that the value of Bf/|f| is not greater than or equal to theupper limit defined in Conditional Formula (10-1), the back focus can beprevented from becoming excessively long, and therefore miniaturizationcan be achieved.

4.0<Bf/|f|  (10)

5.0<Bf/|f|<20.0   (10-1)

wherein Bf is the back focus of the entire projection optical system (anair converted length), and f is the focal length of the entireprojection optical system.

In addition, it is preferable for a principal light ray at the maximumangle of view and the optical axis of the second optical system G2 tointersect between the first lens group G21 and the second lens groupG22. The size of the second optical path bending means R2 which isprovided in the second optical system can be miniaturized by adoptingsuch a configuration.

In addition, the intermediate image may be configured such that theperipheral portion has more field curvature toward the first opticalsystem than the portion thereof at the center of the optical axis. Inthis manner, by keeping distortion, astigmatism, and the like in thefirst optical system G1 and canceling these aberrations in the secondoptical system G2 instead of correcting aberrations in the first opticalsystem G1 and the second optical system G2 independently, it becomespossible to favorably correct various aberrations even with a smallnumber of lenses while achieving a widening of the angle of view.

In addition, it is preferable for the first optical path bending meansand/or the second optical path bending means to be a mirror. Byemploying mirrors in this manner, light loss due to the transmissivityof members will not occur, heat will influence the optical path bendingmeans less, and the optical path bending means can be formed to belightweight, when compared to a case in which prisms are employed. Forthese reasons, employing mirrors is advantageous from the viewpoints ofproperties and productivity in the case that each of the optical pathbending means is configured to perform horizontal reflection or verticalreflection.

In addition, it is preferable for the first optical path bending meansand/or the second optical path bending means to be provided to bend theoptical path 90 degrees. By adopting such a configuration,miniaturization of the projection optical system as a whole can beefficiently achieved.

In addition, it is preferable for images which are displayed by theimage display elements to be projected as magnified images which areinverted by 180 degrees. By adopting such a configuration, the size ofthe system as a whole that includes a screen and the projection opticalsystem can be miniaturized.

Next, examples of numerical values of the projection optical system ofthe present disclosure will be described.

First, the projection optical system according to Example 1 will bedescribed. FIG. 1 is a sectional diagram that illustrates theconfiguration of the projection optical system according to Example 1.Note that in FIG. 1 and in FIGS. 2 through 7 that correspond to Examples2 through 7 to be described later, the side of the image display surfaceSim is the reduction side, and the side of a final lens L32 (a finallens L34 only in Example 5) within the second optical system is themagnification side. The aperture stops St illustrated in the drawings donot necessarily represent the sizes or shapes thereof, but the positionsthereof along the optical axis Z. In addition, FIGS. 1 through 7 alsoshow axial light beams wa and light beams wb at a maximum angle of view.

The projection optical system according to Example 1 is constituted by,in order from the reduction side to the magnification side, the firstoptical system G1, the first optical path bending means R1, and thesecond optical system G2. The first optical system G1 is constituted byten lenses, which are lenses L1 through L10, and the second opticalsystem G2 is constituted by twelve lenses, which are lenses L21 throughL32. In addition, the second optical system G2 is constituted by, inorder from the reduction side to the magnification side, the first lensgroup G21, the second optical path bending means R2, and the second lensgroup G22. The first lens group G21 is constituted by six lenses, whichare lenses L21 through L26, and the second lens group G22 is constitutedby six lenses, which are lenses L27 through L32.

Basic lens data of the projection optical system according to Example 1are shown in Table 1, data related to various items are shown in Table2, and data related to aspherical surface coefficients are shown inTable 3. The meanings of the symbols in the tables will be describedwith those related to Example 1 as an example. However, they arebasically same for Examples 2 through 7 as well.

In the lens data of Table 1, surface numbers that sequentially increasefrom the magnification side to the reduction side, with the surfacetoward the magnification side of the constituent element at the mostmagnification side designated as first, are shown in the column “SurfaceNumber”. The radii of curvature of each of these surfaces are shown inthe column “Radius of Curvature”. The distances between each surface anda next surface are shown in the column “Distance”. The refractiveindices with respect to the d line (wavelength: 587.6 nm) of each of theoptical elements are shown in the column “nd”. The Abbe's numbers ofeach of the optical elements with respect to the d line (wavelength:587.6 nm) are shown in the column “vd”. Here, the signs of the radii ofcurvature are positive in cases that the surface shape is convex towardthe object side, and negative in cases that the surface shape is convextoward the image side. Table 1 also shows the aperture stop St and theoptical member PP. Text reading “(stop)” is shown along with the surfacenumber in the row in the column of surface numbers corresponding to thesurface of the aperture stop St.

The values of the focal length f, the back focus Bf, the F value FNo.,and the full angle of view 2ω are shown as data related to various itemsin Table 2.

Note that the numerical values of the basic lens data and the datarelated to various items are those which are normalized such that theabsolute value of the focal length of the entire projection opticalsystem becomes 1. In addition, the numerical values in each of thetables are rounded off at a predetermined number of digits.

In the lens data of Table 1, an “*” is indicated along with the surfacenumbers of aspherical surfaces, and numerical values related to theparaxial radii of curvature are shown in the column that shows the radiiof curvature for the aspherical surfaces. The data related to asphericalsurface coefficients of Table 3 shows the surface numbers of theaspherical surfaces and aspherical surface coefficients related to theaspherical surfaces. The aspherical surface coefficients are thecoefficients KA and Am (m=3˜17) represented by the aspherical surfaceshape formula below.

${Zd} = {\frac{C \times h^{2}}{1 + \sqrt{1 - {{KA} \times C^{2} \times h^{2}}}} + {\sum\limits_{m}^{\;}{{Am} \times h^{m}}}}$

wherein: Zd is the depth of the aspherical surface (the length of anormal line from a point on an aspherical surface at a height h to aplane perpendicular to the optical axis that contacts the peak of theaspherical surface), h is the height (the distance from the optical axisto the surface of the lens), C is the paraxial curvature, and KA and Amare aspherical surface coefficients (m=3˜17).

TABLE 1 Example 1: Lens Data Surface Radius of Number Curvature Distancend νd *1 −6.0454 0.7622 1.49100 57.58 *2 −23.1701 0.8901 3 17.24560.5145 1.80610 40.93 4 5.6254 1.3385 5 9.4485 0.3810 1.80610 33.27 64.4487 2.4299 7 −13.0249 0.3047 1.77250 49.60 8 7.9549 3.5242 9 37.34013.8111 1.64769 33.79 10 −9.8610 0.3711 11 12.3243 0.8198 1.80518 25.4212 49.0021 4.9115 13 ∞ 0.0000 Second optical path bending means 14 ∞3.8110 15 41.0416 0.2494 1.80518 25.42 16 5.6876 2.2334 1.59282 68.62 17−8.3664 0.0379 18 11.0541 2.4421 1.72916 54.68 19 −4.7277 0.4579 1.8051825.42 20 13.4072 1.8900 *21 20.2550 0.9529 1.51007 56.24 *22 1984.76522.3243 23 156.9733 1.4636 1.80518 25.42 24 −11.3871 10.0606 25 ∞ 0.0000First optical path bending means 26 ∞ 3.6204 *27 −6.4082 0.9529 1.4910057.58 *28 −6.4862 0.0952 29 −23.8508 0.4307 1.80518 25.42 30 14.69433.7034 1.77250 49.60 31 −13.4010 0.0379 32 14.1100 2.2807 1.77250 49.6033 −47.6613 3.1484 34 6.6271 1.1795 1.80400 46.58 35 25.2352 0.23831.51742 52.43 36 3.4758 3.9425 37(stop) ∞ 0.3237 38 −3.4327 0.19231.80518 25.42 39 6.5801 0.9770 1.59282 68.62 40 −4.1078 2.6800 41−41.8171 1.3861 1.51633 64.14 42 −5.2781 0.0379 43 9.7434 1.2004 1.8051825.42 44 −59.6891 3.3573 45 ∞ 4.7637 1.51633 64.14 46 ∞ Second opticalpath bending means positioned at 4.9115 toward the reduction side fromthe 12th surface First optical path bending means positioned at 10.0606toward the reduction side from the 22nd surface

TABLE 2 Example 1: Items (d line) f −1.00 Bf 6.50 FNo. 2.00 2ω[°] 137.4

TABLE 3 Example 1: Aspherical Surface coefficients Surface Number 1 2 21KA −8.5831337E−01   1.5267730E+00  1.0000000E+00 A3 1.3500124E−02 1.6207700E−02  0.0000000E+00 A4 3.7355108E−03 −1.5811440E−03 7.2756257E−03 A5 −1.5958047E−03  −2.6343865E−05 −1.1125847E−03 A61.6144623E−04  4.6257457E−05 −4.3853690E−04 A7 1.9376746E−05−9.1010163E−06 −9.6686212E−05 A8 −5.4169501E−06  −1.1093364E−07−1.2964384E−06 A9 7.3993426E−08  2.0922090E−07  3.4086512E−05 A108.4962283E−08 −1.0107572E−08 −2.7066187E−06 A11 −6.8422640E−09 −2.0627751E−09 −3.3282322E−06 A12 −4.7910538E−10   1.4750183E−10 4.6361979E−07 A13 7.9463074E−11  9.8397311E−12  1.5667589E−07 A14−7.6995814E−13  −8.1234981E−13 −2.1732042E−08 A15 −2.9134071E−13 −1.8967333E−14 −3.6501692E−09 A16 1.1711185E−14  1.5857063E−15 3.3018889E−10 A17 — —  3.3724534E−11 Surface Number 22 27 28 KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 A3  1.1570968E−181.4379200E−18 0.0000000E+00 A4  1.1017431E−02 1.5339083E−031.0017244E−03 A5  6.3653027E−04 −1.5364843E−04  1.6329654E−04 A6−1.5459887E−03 7.5849186E−05 −1.1437954E−04  A7 −6.7282664E−056.4644403E−05 7.8011554E−05 A8  1.4511524E−04 −3.0470719E−05 −9.1645167E−06  A9 −1.3328630E−05 −1.8064302E−06  −6.8267502E−06  A10−8.8345669E−06 2.5038294E−06 1.8502503E−06 A11  2.4349490E−06−1.5479839E−07  1.6669133E−07 A12  2.9922618E−07 −9.3616561E−08 −1.0039622E−07  A13 −1.5541144E−07 1.1174150E−08 2.8772081E−09 A14−3.4183472E−09 1.6690407E−09 2.3388596E−09 A15  4.5654529E−09−2.6272163E−10  −1.8625879E−10  A16 −2.6343230E−11 −1.1361384E−11 −2.0187141E−11  A17 −5.2171013E−11 2.1681971E−12 2.1924717E−12

Diagrams that illustrate various aberrations of the projection opticalsystem according to Example 1 are illustrated in FIG. 8. The sphericalaberration, the astigmatism, the distortion, and the lateral chromaticaberration are illustrated in order from the left side of the drawingsheet of FIG. 8. The diagrams that illustrate spherical aberration,astigmatism, and distortion show aberrations that have the d line(wavelength: 587.6 nm) as a reference wavelength. The diagram thatillustrates spherical aberration shows aberrations related to the d line(wavelength: 587.6 nm), the C line (wavelength: 656.3 nm), and the Fline (wavelength: 486.1 nm) indicated by a solid line, a long brokenline, and a short broken line, respectively. In the diagrams thatillustrate astigmatism, aberrations related to the d line in thesagittal direction and the tangential direction are indicated by a solidline and a short broken line, respectively. In the diagram thatillustrates lateral chromatic aberration, aberrations related to the Cline (wavelength: 656.3 nm) and the F line (wavelength: 486.1 nm) areindicated by a long broken line and a short broken line, respectively.In the diagrams that illustrate spherical aberration, “FNo.” denotes Fnumbers, and in the diagrams that illustrate other aberrations, “ω”denotes half angles of view.

Note that the numerical values shown in the basic lens data and the datarelated to various items as well as the diagrams that illustrateaberrations are all those for a finite projection distance. The datarelated to Example 1 are those for a case in which the projectiondistance is 121.950.

The symbols, meanings, and the manner in which each type of data areshown in the description of Example 1 above are the same for thefollowing Examples unless particularly noted. Therefore, redundantdescriptions will be omitted below.

Next, a projection optical system according to Example 2 will bedescribed. FIG. 2 is a sectional diagram that illustrates theconfiguration of the projection optical system according to Example 2.The projection optical system according to Example 2 is the same as thataccording to Example 1, except that a first optical system G1 isconstituted by nine lenses, which are lenses L1 through L9. In addition,basic lens data are shown in Table 4, data related to various items areshown in Table 5, data related to aspherical surface coefficients areshown in Table 6, and diagrams that illustrate aberrations areillustrated in FIG. 9 for the projection optical system according toExample 2. For Example 2, data are shown for a case in which theprojection distance is 121.933.

TABLE 4 Example 2: Lens Data Surface Radius of Number Curvature Distancend νd *1 −5.8925 0.7620 1.49100 57.58 *2 −20.1570 0.8369 3 15.55650.5142 1.80610 33.27 4 5.6978 1.4192 5 10.0304 0.3809 1.80400 46.58 64.1382 2.5409 7 −11.8212 0.3047 1.69680 55.53 8 7.4250 3.2265 9 21.67973.8106 1.62588 35.70 10 −9.6963 0.6623 11 13.0592 0.7299 1.80518 25.4212 45.3570 4.9674 13 ∞ 0.0000 Second optical path bending means 14 ∞3.8104 15 29.4001 0.2494 1.80518 25.42 16 5.7492 2.3083 1.59282 68.62 17−8.9476 0.0379 18 10.9153 2.5665 1.72916 54.68 19 −4.9491 0.2761 1.8051825.42 20 13.1774 1.9787 *21 37.8174 0.9528 1.51007 56.24 *22 −42.80782.1168 23 28.9497 1.5439 1.80518 25.42 24 −15.3485 11.3838 25 ∞ 0.0000First optical path bending means 26 ∞ 5.3346 *27 −6.8136 0.9524 1.4910057.58 *28 −6.3119 0.0953 29 26.6794 0.4304 1.80518 25.42 30 11.96382.9976 1.80400 46.58 31 −15.6135 2.2913 32 6.2479 1.9616 1.79952 42.2233 −19.3391 0.2380 1.75520 27.51 34 4.7254 4.1465 35(stop) ∞ 1.2584 36−2.9686 0.1922 1.69895 30.13 37 7.6474 1.1974 1.49700 81.54 38 −4.55341.1333 39 −56.3920 1.5180 1.51633 64.14 40 −4.8487 0.0379 41 9.88911.2337 1.80518 25.42 42 −43.9166 3.3192 43 ∞ 4.7630 1.51633 64.14 44 ∞Second optical path bending means positioned at 4.9674 toward thereduction side from the 12th surface First optical path bending meanspositioned at 11.3838 toward the reduction side from the 22nd surface

TABLE 5 Example 2: Items (d line) f −1.00 Bf 6.50 FNo. 2.00 2ω [°] 137.4

TABLE 6 Example 2: Aspherical Surface coefficients Surface Number 1 2 21KA −9.1567984E−01  1.4161570E+00 1.0000000E+00 A3 1.2952037E−021.5904415E−02 0.0000000E+00 A4 3.9150390E−03 −1.3949854E−03 9.3942194E−03 A5 −1.5698458E−03  4.4581928E−05 −1.4325021E−03  A61.5067101E−04 3.6644074E−05 −7.4380791E−04  A7 1.9408238E−05−1.1288892E−05  4.8872772E−05 A8 −5.1447424E−06  9.4146166E−081.0656305E−05 A9 5.4632195E−08 2.4324539E−07 1.0315634E−05 A108.1696007E−08 −1.2116421E−08  −5.7754042E−07  A11 −6.3994138E−09 −2.3676359E−09  −1.3572625E−06  A12 −4.6802337E−10  1.5599848E−101.7149721E−07 A13 7.5394399E−11 1.1315205E−11 6.9656284E−08 A14−6.7157046E−13  −8.1910668E−13  −8.7243284E−09  A15 −2.7762688E−13 −2.1842079E−14  −1.7008941E−09  A16 1.1039658E−14 1.5599543E−151.3147816E−10 A17 — — 1.6357442E−11 Surface Number 22 27 28 KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 A3  0.0000000E+000.0000000E+00 0.0000000E+00 A4  1.3217033E−02 1.0973771E−037.2353797E−04 A5 −3.8764052E−05 −1.6119120E−04  3.1890659E−04 A6−1.3457239E−03 9.2374493E−05 −2.1155652E−04  A7 −2.5284883E−052.6448831E−05 8.5393245E−05 A8  5.9734739E−05 −2.2364856E−05 −9.6262302E−07  A9 −3.4756794E−07 1.0647077E−06 −9.5399408E−06  A10 1.0993936E−07 1.4823302E−06 1.9030259E−06 A11  2.3308460E−07−2.0231799E−07  3.2394660E−07 A12 −1.3176092E−07 −4.5293765E−08 −1.2798209E−07  A13 −1.4357380E−08 8.8634300E−09 3.6171844E−10 A14 5.8120548E−09 6.4024409E−10 3.3681773E−09 A15  3.6457202E−10−1.6537919E−10  −2.1991630E−10  A16 −8.6133307E−11 −3.1465255E−12 −3.1913698E−11  A17 −3.5469901E−12 1.1501260E−12 3.1394043E−12

Next, a projection optical system according to Example 3 will bedescribed. FIG. 3 is a sectional diagram that illustrates theconfiguration of the projection optical system according to Example 3.The projection optical system according to Example 3 is the same as thataccording to Example 1, except that a first optical system G1 isconstituted by nine lenses, which are lenses L1 through L9. In addition,basic lens data are shown in Table 7, data related to various items areshown in Table 8, data related to aspherical surface coefficients areshown in Table 9, and diagrams that illustrate aberrations areillustrated in FIG. 10 for the projection optical system according toExample 3. For Example 3, data are shown for a case in which theprojection distance is 121.682.

TABLE 7 Example 3: Lens Data Surface Radius of Number Curvature Distancend νd *1 −5.9537 0.7607 1.49100 57.58 *2 −22.4102 1.1909 3 15.51820.5135 1.77250 49.60 4 5.7832 1.5272 5 10.9610 0.3801 1.77250 49.60 64.1302 2.6498 7 −9.7742 0.3044 1.58913 61.13 8 7.6108 3.1655 9 31.35013.8027 1.60342 38.03 10 −9.3384 0.5129 11 11.5048 0.7443 1.80518 25.4212 37.5734 3.9396 13 ∞ 0.0000 Second optical path bending means 14 ∞3.8026 15 118.7760 0.2492 1.80518 25.42 16 5.6890 2.5387 1.59282 68.6217 −6.8714 0.0382 18 10.3143 2.6702 1.65160 58.55 19 −5.0732 1.55131.80518 25.42 20 11.7432 0.9153 *21 −85.1980 0.9506 1.51007 56.24 *22−15.9578 2.6015 23 79.1298 2.3027 1.80518 25.42 24 −9.1227 10.7955 25 ∞0.0000 First optical path bending means 26 ∞ 2.8519 27 −30.0089 0.42961.80518 25.42 28 8.9423 3.7247 1.60562 43.71 29 −10.7747 0.0380 3014.8618 1.7323 1.80400 46.58 31 −43.2477 2.5494 32 6.8161 1.7763 1.8040046.58 33 −18.9168 0.2378 1.51742 52.43 34 3.5606 3.6937 35(stop) ∞0.4566 36 −3.1391 0.1921 1.80518 25.42 37 5.7762 1.0367 1.59282 68.62 38−4.3960 0.8015 39 −185.9641 3.5097 1.48749 70.24 40 −5.0890 0.0382 418.7749 1.2786 1.80518 25.42 42 −82.3017 3.3434 43 ∞ 4.7532 1.51633 64.1444 ∞ Second optical path bending means positioned at 3.9396 toward thereduction side from the 12th surface First optical path bending meanspositioned at 10.7955 toward the reduction side from the 22nd surface

TABLE 8 Example 3: Items (d line) f −1.00 Bf 6.49 FNo. 2.00 2ω [°] 137.2

TABLE 9 Example 3: Aspherical Surface Coefficients Surface Number 1 2 21KA −9.7838303E−01  −2.6347599E−02 1.0000000E+00 A3 1.7745692E−02 2.2903118E−02 0.0000000E+00 A4 3.1804157E−03 −3.0350282E−031.1028892E−02 A5 −1.8105557E−03   3.3186241E−05 −3.4560622E−03  A62.1912345E−04  1.0526652E−04 6.7953883E−04 A7 2.2206788E−05−1.9795493E−05 3.3574732E−04 A8 −7.4954415E−06  −1.0039607E−06−3.6915532E−04  A9 1.6658017E−07  4.9003027E−07 3.3471927E−05 A101.1584383E−07 −6.9036888E−09 4.0859303E−05 A11 −9.7504792E−09 −5.3997242E−09 −8.1250707E−06  A12 −6.5436739E−10   1.9679141E−10−2.0676654E−06  A13 1.0811525E−10  2.8987621E−11 5.7889510E−07 A14−8.7836424E−13  −1.3215137E−12 5.0174747E−08 A15 −3.8863108E−13 −6.2055308E−14 −1.8562606E−08  A16 1.4852258E−14  2.9502248E−15−4.6261415E−10  A17 — — 2.3023163E−10 Surface Number 22 KA 1.0000000E+00A3 0.0000000E+00 A4 1.1686461E−02 A5 1.1628046E−03 A6 −2.3602068E−03  A79.5211393E−04 A8 6.5610185E−05 A9 −2.3291961E−04  A10 4.7859293E−05 A111.7803555E−05 A12 −6.5699490E−06  A13 −3.1176802E−07  A14 3.2974300E−07A15 −1.8680233E−08  A16 −5.8711149E−09  A17 6.3669476E−10

Next, a projection optical system according to Example 4 will bedescribed. FIG. 4 is a sectional diagram that illustrates theconfiguration of the projection optical system according to Example 4.The configuration of the projection optical system according to Example4 is the same as that according to Example 1. In addition, basic lensdata are shown in Table 10, data related to various items are shown inTable 11, data related to aspherical surface coefficients are shown inTable 12, and diagrams that illustrate aberrations are illustrated inFIG. 11 for the projection optical system according to Example 4. ForExample 4, data are shown for a case in which the projection distance is121.811.

TABLE 10 Example 4: Lens Data Surface Radius of Number CurvatureDistance nd νd *1 −6.9306 0.8121 1.49100 57.58 *2 −44.8371 0.5265 313.5687 0.5483 1.80518 25.42 4 6.2556 1.8879 5 14.4551 0.4058 1.7995242.22 6 4.3283 2.5036 7 −15.5363 0.3246 1.80400 46.58 8 8.0372 4.5605 971.2289 2.1682 1.64769 33.79 10 −9.5623 0.3540 11 11.7365 0.8240 1.8051825.42 12 46.7315 5.1903 13 ∞ 0.0000 Second optical path bending means 14∞ 4.0604 15 17.9887 0.2657 1.80518 25.42 16 4.8108 2.2397 1.53775 74.7017 −7.2175 0.0404 18 10.5125 2.3557 1.67790 55.34 19 −4.4440 0.29421.80518 25.42 20 11.1288 0.3251 *21 12.2198 0.8907 1.51007 56.24 *2213.5064 0.3292 23 13.7443 1.6941 1.59282 68.62 24 −9.8049 10.9631 25 ∞0.0000 First optical path bending means 26 ∞ 4.2634 *27 −7.0308 1.01531.51007 56.24 *28 −6.8249 0.1013 29 −21.7935 0.4587 1.80518 25.42 3018.3685 3.6762 1.80400 46.58 31 −12.7408 0.0404 32 18.9842 1.86291.80400 46.58 33 −63.2950 3.1011 34 12.2347 1.6669 1.80400 46.58 35−21.4475 0.2536 1.54814 45.78 36 4.0727 8.1896 37(stop) ∞ 0.8035 38−5.8768 0.2051 1.84666 23.78 39 7.9679 1.0619 1.49700 81.54 40 −5.43174.1679 41 −45.9194 1.5980 1.51633 64.14 42 −6.6372 0.0404 43 17.05601.0803 1.80518 25.42 44 −66.7966 3.6543 45 ∞ 14.1859 1.51633 64.14 46 ∞0.6091 1.50847 61.19 47 ∞ Second optical path bending means positionedat 5.1903 toward the reduction side from the 12th surface First opticalpath bending means positioned at 10.9631 toward the reduction side fromthe 22nd surface

TABLE 11 Example 4: Items (d line) f −1.00 Bf 13.45 FNo. 2.50 2ω[°]139.8

TABLE 12 Example 4: Aspherical Surface Coefficients Surface Number 1 221 KA −9.6578232E−01   7.1797830E+00 1.0000000E+00 A3 1.5152595E−02 1.7786856E−02 0.0000000E+00 A4 2.4745249E−03 −1.8010192E−037.2368068E−03 A5 −1.4192070E−03  −2.1112616E−04 −1.0862983E−03  A61.7031530E−04  5.0422771E−05 −8.5312809E−04  A7 1.4163708E−05−8.7904656E−07 −3.0853539E−04  A8 −4.9232854E−06  −4.3347102E−077.6609049E−05 A9 1.2572919E−07  4.1185022E−08 8.7265414E−05 A106.7186825E−08 −7.9498160E−10 −1.3671151E−05  A11 −5.7701281E−09 −3.3328951E−10 −9.0721375E−06  A12 −3.2588431E−10   3.4304624E−111.5586581E−06 A13 5.7373154E−11  1.0307507E−12 4.7059813E−07 A14−6.4187374E−13  −1.9225952E−13 −7.5089483E−08  A15 −1.8715151E−13 −1.0720720E−15 −1.2172965E−08  A16 7.2850548E−15  3.3466154E−161.2819746E−09 A17 — — 1.2480983E−10 Surface Number 22 27 28 KA1.0000000E+00 1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+000.0000000E+00 A4 1.0409797E−02 2.0896951E−03 1.3888769E−03 A51.3491359E−03 −1.6041807E−05  2.1379246E−04 A6 −2.5137397E−03 −5.7456735E−05  −1.7408475E−04  A7 −3.2541827E−04  2.5117861E−055.2556125E−05 A8 3.4362373E−04 −8.5697549E−06  −2.8508038E−07  A91.9870848E−05 6.4738130E−08 −4.4651233E−06  A10 −2.8029664E−05 7.3456995E−07 9.2310511E−07 A11 2.5095644E−07 −1.1220112E−07 9.9022538E−08 A12 1.3425464E−06 −2.2982349E−08  −5.2005980E−08  A13−7.8570318E−08  5.4013252E−09 1.7527741E−09 A14 −3.3597707E−08 3.0684516E−10 1.1516468E−09 A15 3.2268052E−09 −1.0235851E−10 −9.8561406E−11  A16 3.3008718E−10 −1.2594636E−12  −9.2007459E−12  A17−4.3653244E−11  7.0689178E−13 1.0505968E−12

Next, a projection optical system according to Example 5 will bedescribed. FIG. 5 is a sectional diagram that illustrates theconfiguration of the projection optical system according to Example 5.In the projection optical system according to Example 5, a first opticalsystem G1 is constituted by eight lenses, which are lenses L1 throughL8, a first lens group G21 within a second optical system G2 isconstituted by seven lenses, which are lenses L21 through L27, and asecond lens group G22 is constituted by seven lenses, which are lensesL28 through L34. In addition, basic lens data are shown in Table 13,data related to various items are shown in Table 14, data related toaspherical surface coefficients are shown in Table 15, and diagrams thatillustrate aberrations are illustrated in FIG. 12 for the projectionoptical system according to Example 5. For Example 5, data are shown fora case in which the projection distance is 193.485.

TABLE 13 Example 5: Lens Data Surface Radius of Number CurvatureDistance nd νd *1 −5.6596 0.7533 1.53158 55.08 *2 −16.3802 0.5746 314.3992 0.5991 1.83481 42.72 4 7.2250 2.1723 5 16.5662 0.4452 1.8340037.16 6 5.0703 2.6525 7 −46.4337 0.3425 1.67790 55.34 8 7.4771 2.3614 *9−38.9505 0.9035 1.49100 57.58 *10 −81.9445 4.3890 11 2242.0095 1.62681.56732 42.82 12 −9.5556 0.3537 13 13.7977 0.6579 1.84666 23.78 1436.1136 5.4792 15 ∞ 0.0000 Second optical path bending means 16 ∞ 4.280617 19.1527 0.2928 1.80518 25.46 18 6.0893 2.4380 1.59282 68.62 19−11.9454 0.0427 20 16.0233 2.5802 1.69680 55.53 21 −5.4733 0.27401.72825 28.46 22 6.6027 0.6754 23 13.0660 1.3889 1.49700 81.61 24−15.6033 2.2536 *25 −10.4647 1.0976 1.49100 57.58 *26 −6.7619 1.5735 2746.2663 1.6396 1.84666 23.78 28 −21.0908 13.9124 29 ∞ 0.0000 Firstoptical path bending means 30 ∞ 7.5339 31 −85.4771 0.4486 1.80518 25.4632 13.5453 3.8081 1.54814 45.78 33 −13.3932 0.0341 34 13.1189 2.31871.80400 46.58 35 −86.5640 7.7542 36 4.6327 0.3402 1.53172 48.84 373.4248 1.3953 38(stop) ∞ 1.3698 39 −3.5518 0.2073 1.80518 25.46 4012.7160 1.0861 1.59282 68.62 41 −5.1660 0.8689 42 −60.7625 1.62281.49700 81.61 43 −5.3392 2.3935 44 17.4292 1.2453 1.80809 22.76 45−18.4369 2.9837 46 ∞ 6.7814 1.51633 64.14 47 ∞ Second optical pathbending means positioned at 5.4792 toward the reduction side from the14th surface First optical path bending means positioned at 13.9124toward the reduction side from the 26th surface

TABLE 14 Example 5: Items (d line) f −1.00 Bf 7.46 FNo. 1.90 2ω[°] 146.2

TABLE 15 Example 5: Aspherical Surface Coefficients Surface Number 1 2 9KA −1.1816188E+00  −1.3324618E+01 1.0000000E+00 A3 9.9914448E−03 1.8025934E−02 0.0000000E+00 A4 1.9941605E−03 −1.6590684E−02−3.5796035E−03  A5 −6.2703958E−04   1.6231240E−02 1.0861780E−03 A64.0424283E−05 −1.0738823E−02 1.9213727E−04 A7 5.2426763E−06 4.9447881E−03 −1.6203496E−04  A8 −9.0449589E−07  −1.6200774E−038.1745411E−06 A9 4.0097482E−09  3.8466696E−04 9.9925225E−06 A108.5415190E−09 −6.6958175E−05 −1.3729672E−06  A11 −5.4877705E−10  8.5531167E−06 −2.0453540E−07  A12 −2.5750016E−11  −7.9253815E−074.1005319E−08 A13 3.9725886E−12  5.1808517E−08 −7.5519988E−10  A14−5.7578837E−14  −2.2637072E−09 −3.0968595E−11  A15 −8.8476101E−15  5.9290878E−11 0.0000000E+00 A16 3.3317364E−16 −7.0358287E−130.0000000E+00 A17 — — 0.0000000E+00 Surface Number 10 25 26 KA1.0000000E+00  1.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 0.0000000E+00 A4 −2.0633751E−03   6.5744572E−039.5826426E−03 A5 5.0576859E−04 −1.5664386E−03 −1.7691499E−03  A62.2728842E−04 −8.1425427E−04 −5.2488705E−04  A7 −1.2340116E−04  2.8588920E−04 1.3275678E−04 A8 6.1449182E−07  4.3874670E−051.7872875E−05 A9 9.7487777E−06 −3.0501761E−05 −4.4079773E−06  A10−1.5115907E−06  −4.7115824E−07 −6.1994851E−07  A11 −1.5091304E−07  2.0101846E−06 3.4847902E−08 A12 5.8002139E−08 −1.0264767E−071.7662157E−08 A13 −6.8430174E−09  −8.0165715E−08 1.9499489E−09 A144.4980543E−10  5.6191783E−09 −2.2111521E−10  A15 0.0000000E+00 1.7533315E−09 −5.4715476E−11  A16 0.0000000E+00 −8.4020597E−115.5653886E−13 A17 0.0000000E+00 −1.5951602E−11 4.2354510E−13

Next, a projection optical system according to Example 6 will bedescribed. FIG. 6 is a sectional diagram that illustrates theconfiguration of the projection optical system according to Example 6.The projection optical system according to Example 6 is the same as thataccording to Example 1, except that a first optical system G1 isconstituted by nine lenses, which are lenses L1 through L9. In addition,basic lens data are shown in Table 16, data related to various items areshown in Table 17, data related to aspherical surface coefficients areshown in Table 18, and diagrams that illustrate aberrations areillustrated in FIG. 13 for the projection optical system according toExample 6. For Example 6, data are shown for a case in which theprojection distance is 193.308.

TABLE 16 Example 6: Lens Data Surface Radius of Number CurvatureDistance nd νd *1 −7.8431 0.8210 1.53158 55.08 *2 −40.3388 0.2762 313.5021 0.5986 1.83400 37.16 4 7.2749 2.0717 5 15.5196 0.4446 1.8040046.58 6 5.0340 2.8719 7 −20.9879 0.3591 1.77250 49.60 8 8.9222 8.5533 9564.7144 0.9891 1.54814 45.78 10 −12.7779 0.4910 11 13.4910 0.79181.84666 23.78 12 88.8120 5.2780 13 ∞ 0.0000 Second optical path bendingmeans 14 ∞ 4.2767 15 16.1687 0.2924 1.80518 25.42 16 5.6967 2.14781.49700 81.54 17 −10.8982 0.0426 18 9.2883 2.6961 1.77250 49.60 19−4.9601 0.2738 1.80518 25.42 20 6.5971 2.1956 *21 117.6592 1.19761.49100 57.58 *22 −20.1220 2.0104 23 23.1638 2.0712 1.80518 25.42 24−16.0224 10.8979 25 ∞ 0.0000 First optical path bending means 26 ∞4.7899 *27 −6.8792 1.1976 1.49100 57.58 *28 −7.0459 6.2838 29 439.38110.4653 1.80518 25.42 30 11.6780 3.6301 1.77250 49.60 31 −21.3793 0.034432 10.1113 1.8923 1.83481 42.72 33 36.7596 5.2069 34 4.1405 0.23961.54814 45.78 35 2.9701 2.6461 36(stop) ∞ 0.7601 37 −3.6394 0.20701.80518 25.42 38 7.2962 1.0283 1.59282 68.62 39 −4.3434 2.6611 40−25.8763 1.6263 1.48749 70.24 41 −5.1461 0.0343 42 13.4402 1.18421.80809 22.76 43 −38.5360 2.9797 44 ∞ 6.7752 1.51633 64.14 45 ∞ Secondoptical path bending means positioned at 5.2780 toward the reductionside from the 12th surface First optical path bending means positionedat 10.8979 toward the reduction side from the 22nd surface

TABLE 17 Example 6: Items (d line) f −1.00 Bf 7.44 FNo. 2.15 2ω (°)144.0

TABLE 18 Example 6: Aspherical Surface Coefficients Surface Number 1 221 KA −8.6374673E−01  2.8058941E+00 1.0000000E+00 A3 1.0892111E−021.3536870E−02 0.0000000E+00 A4 2.0602299E−03 −1.7423092E−03 7.6281741E−03 A5 −8.4137148E−04  1.4102816E−04 −1.6584501E−03  A68.4099509E−05 3.0740117E−05 −1.0742824E−04  A7 6.2292141E−06−1.0742136E−05  1.2151217E−04 A8 −1.9915067E−06  2.1190422E−07−7.1304107E−05  A9 5.8146838E−08 1.8001317E−07 4.9527146E−06 A102.1536466E−08 −9.8113054E−09  6.6513222E−06 A11 −1.8578714E−09 −1.4131917E−09  −1.1932142E−06  A12 −7.7044970E−11  9.7692964E−11−2.7738852E−07  A13 1.4424950E−11 5.4836221E−12 6.8601540E−08 A14−1.9347377E−13  −4.1353110E−13  6.5114905E−09 A15 −3.7177479E−14 −8.5800894E−15  −1.7418222E−09  A16 1.3629548E−15 6.4708517E−16−7.0262339E−11  A17 — — 1.6869216E−11 Surface Number 22 27 28 KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 A3  0.0000000E+000.0000000E+00 0.0000000E+00 A4  9.6085359E−03 7.0444903E−045.7465459E−04 A5 −4.5097270E−04 2.1717416E−05 −9.3658722E−05  A6−5.7756899E−04 −6.2182315E−05  −1.5628839E−05  A7  1.3491746E−045.9343722E−05 4.4605724E−05 A8 −1.7133910E−05 −9.4771050E−06 −9.4703870E−06  A9 −1.4555806E−05 −3.5657278E−06  −2.0686945E−06  A10 4.4644466E−06 1.1643902E−06 8.7408667E−07 A11  6.7813254E−074.5757831E−08 6.9936703E−09 A12 −2.6297019E−07 −4.7738954E−08 −3.1431820E−08  A13 −1.2159623E−08 2.1012941E−09 1.8298205E−09 A14 6.9761449E−09 8.6855543E−10 5.1961946E−10 A15 −2.4056727E−11−7.1980760E−11  −4.7665745E−11  A16 −7.0658022E−11 −5.9292827E−12 −3.2693494E−12  A17  2.2005904E−12 6.3049866E−13 3.7035392E−13

Next, a projection optical system according to Example 7 will bedescribed. FIG. 7 is a sectional diagram that illustrates theconfiguration of the projection optical system according to Example 7.The projection optical system according to Example 7 is the same as thataccording to Example 1, except that a first optical system G1 isconstituted by eight lenses, which are lenses L1 through L8. Inaddition, basic lens data are shown in Table 19, data related to variousitems are shown in Table 20, data related to aspherical surfacecoefficients are shown in Table 21, and diagrams that illustrateaberrations are illustrated in FIG. 14 for the projection optical systemaccording to Example 7. For Example 7, data are shown for a case inwhich the projection distance is 193.142.

TABLE 19 Example 7: Lens Data Surface Radius of Number CurvatureDistance nd νd *1 −8.8721 0.7519 1.49100 57.58 *2 −254.6544 0.6815 314.7212 0.5981 1.80400 46.58 4 7.0737 2.0265 5 15.1030 0.4442 1.8040046.58 6 4.9512 2.7912 7 −22.6376 0.3420 1.80400 46.58 8 9.8694 7.9726 9810.9992 1.1266 1.57501 41.50 10 −11.9105 1.0465 11 12.8543 0.72931.84666 23.78 12 44.9139 5.5874 13 ∞ 0.0000 Second optical path bendingmeans 14 ∞ 4.2731 15 28.9195 0.2924 1.80518 25.46 16 5.9219 2.37321.59282 68.62 17 −11.6693 0.0427 18 10.6865 2.7535 1.77250 49.60 19−5.3121 0.2734 1.80518 25.46 20 8.9458 2.2138 *21 31.5562 1.1966 1.4910057.58 *22 −35.3204 3.0720 23 32.6385 1.9133 1.84666 23.78 24 −16.359812.2873 25 ∞ 0.0000 First optical path bending means 26 ∞ 5.8114 *27−7.1825 1.1966 1.49100 57.58 *28 −6.6518 1.2347 29 −15.9865 0.44801.80518 25.46 30 17.6459 3.3889 1.77250 49.60 31 −13.5422 0.0340 3215.3862 2.0644 1.83481 42.72 33 −63.0485 8.7700 34(stop) ∞ 1.4720 35−3.9554 0.2067 1.80518 25.46 36 7.9139 2.5513 1.49700 81.61 37 −7.11580.0340 38 2527.1384 2.2751 1.49700 81.61 39 −5.8089 0.0340 40 14.71151.1539 1.80809 22.76 41 −24.8086 2.9766 42 ∞ 6.7694 1.51633 64.14 43 ∞Second optical path bending means positioned at 5.5874 toward thereduction side from the 12th surface First optical path bending meanspositioned at 12.2873 toward the reduction side from the 22nd surface

TABLE 20 Example 7: Items (d line) f −1.00 Bf 7.44 FNo. 1.90 2ω [°]143.8

TABLE 21 Example 7: Aspherical Surface Coefficients Surface Number 1 221 KA −9.7629926E−01  −1.0121161E+15 1.0000000E+00 A3 1.0866457E−02 1.1735264E−02 0.0000000E+00 A4 1.2868927E−03 −1.4797870E−036.1198322E−03 A5 −6.7290615E−04  −2.3225992E−06 −1.4131764E−03  A67.8702501E−05  2.8097790E−05 −2.7703398E−04  A7 3.3166760E−06−3.5929021E−06 5.0964556E−05 A8 −1.5818367E−06  −9.1972990E−085.4732107E−06 A9 7.2167764E−08  5.4110745E−08 −5.9529727E−07  A101.4205009E−08 −1.9718799E−09 −1.4406845E−06  A11 −1.4904643E−09 −3.4590147E−10 2.1870466E−07 A12 −3.4313829E−11   2.1659611E−111.1543151E−07 A13 9.7906392E−12  1.0456182E−12 −2.1652483E−08  A14−1.9373000E−13  −8.2794522E−14 −2.9163771E−09  A15 −2.2174334E−14 −1.2553008E−15 7.4125754E−10 A16 8.7986626E−16  1.0971963E−162.1213106E−11 A17 — — −8.6988400E−12  Surface Number 22 27 28 KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 A3  0.0000000E+000.0000000E+00 0.0000000E+00 A4  9.7023658E−03 4.5207917E−045.4793408E−04 A5 −8.6522764E−04 4.8773125E−04 2.1179068E−04 A6−6.3276099E−04 −1.1315321E−04  −3.2973787E−05  A7  1.0747981E−04−1.4901296E−05  2.6130398E−06 A8 −1.1031205E−06 1.0410665E−05−2.2356759E−06  A9 −8.5955520E−06 −7.9284129E−08  7.2361539E−07 A10 2.4677641E−06 −5.6734762E−07  1.3692429E−07 A11  3.7054306E−073.4763323E−08 −7.4515410E−08  A12 −1.4276631E−07 1.8251511E−081.2476395E−09 A13 −7.8425486E−09 −1.6251086E−09  2.2957361E−09 A14 3.5183434E−09 −3.1272447E−10  −1.5632446E−10  A15  6.6949249E−113.2910950E−11 −2.5652373E−11  A16 −3.2820464E−11 2.1959051E−122.1041002E−12 A17 −7.0996642E−14 −2.4958836E−13  5.5467468E−14

Table 22 shows values corresponding to Conditional Formulae (1) through(10) for the projection optical systems according to Examples 1 through7. Note that all of the Examples use the d line as a referencewavelength, and the values shown in Table 22 are related to thereference wavelength.

TABLE 22 Formula Condition Example 1 Example 2 Example 3 Example 4Example 5 (1) TL1/|f| 22.81 19.68 21.50 29.32 24.89 (2) TL21/|f| 12.0512.03 13.82 8.43 14.26 (3) D12/|f| 13.68 16.72 13.65 15.23 21.45 (4)D212/|f| 8.72 8.78 7.74 9.25 9.76 (5) f2/|f| 1.86 1.79 1.89 1.54 1.80(6) Imφ · f2/f² 9.56 9.20 9.70 8.44 12.11 (7) enP/TL2 0.117 0.117 0.1200.132 0.112 (8) Imφ/TL2 0.143 0.143 0.138 0.168 0.161 (9) f22/f21 1.131.38 1.18 1.08 0.61 (10) Bf/|f| 6.50 6.50 6.49 13.45 7.46 FormulaCondition Example 6 Example 7 (1) TL1/|f| 29.10 24.86 (2) TL21/|f| 12.9314.13 (3) D12/|f| 15.69 18.10 (4) D212/|f| 9.55 9.86 (5) f2/|f| 1.911.92 (6) Imφ · f2/f² 11.75 11.79 (7) enP/TL2 0.117 0.116 (8) Imφ/TL20.151 0.144 (9) f22/f21 0.61 0.73 (10) Bf/|f| 7.44 7.44

Based on the above data, it can be understood that all of the projectionoptical systems according to Examples 1 through 7 satisfy ConditionalFormulae (1) through (5), and are projection optical systems having highprojection performance having wide angles of view of 135° or greater,that favorably correct various aberrations while achievingminiaturization.

Next, an embodiment of a projection type display device of the presentdisclosure will be described with reference to FIG. 15. FIG. 15 is aschematic diagram that illustrates a projection type display deviceaccording to the embodiment of the present disclosure.

The projection type display device 100 illustrated in FIG. 15 isequipped with: a projection optical system 10 according to an embodimentof the present disclosure; a light source 20; transmissive displayelements 11 a through 11 c that function as light valves eachcorresponding to a colored light beam; and an illuminating opticalsection 30 that guides a light beam form the light source 20 to thelight valves. The illuminating optical section has: dichroic mirrors 12and 13 for separating colors; a cross dichroic prism 14 for combiningcolors; condenser lenses 16 a through 16 c; and total reflection mirrors18 a through 18 c. Note that the projection optical system 10 isschematically illustrated in FIG. 15. In addition, although notillustrated in FIG. 15, an integrator such as a fly eye is providedbetween the light source 20 and the dichroic minor 12.

White light output by the light source 20 is separated into threecolored light beams (G light, B light, and R light) by the dichroicminors 12 and 13. The optical paths of the colored light beams aredeflected by the total reflection minors 18 a through 18 c, then thecolored light beams enter the transmissive display elements 11 a through11 c corresponding thereto via the condenser lenses 16 a through 16 cand are optically modulated. After the colors are combined by the crossdichroic prism 14, the combined light beam enters the projection opticalsystem 10. The projection optical system 10 projects an optical imageformed by light which has been optically modulated by the transmissivedisplay elements 11 a through 11 c onto a screen (not shown).

Transmissive liquid crystal display elements, for example, may beemployed as the transmissive display elements 11 a through 11 c. Notethat FIG. 15 illustrates an example in which transmissive displayelements are employed as the light valves. However, the light valves tobe provided in the projection type display device of the presentdisclosure are not limited to transmissive display elements, and otherlight modulating means such as reflective liquid crystal displayelements and DMD's may alternatively be employed.

The projection type display device 100 of the present embodiment isequipped with the projection optical system 10 of the presentdisclosure. Therefore, the apparatus can be miniaturized, while highquality images can be projected at wide angles of view.

The present disclosure has been described with reference to theembodiments and Examples thereof. However, the present disclosure is notlimited to the above embodiments and Examples, and various modificationsare possible. For example, the values of the radii of curvature, thedistances among surfaces, the refractive indices, the Abbe's numbers,and the aspherical surface coefficients of the lenses are not limited tothose indicated in the above Examples, and may be other values.

1. A projection optical system that forms an intermediate image at aposition conjugate to an image displayed by an image display elementprovided on a reduction side conjugate plane, and projects theintermediate image onto a magnification side conjugate plane as amagnified image, the projection optical system comprising: a pluralityof lenses; and two optical path bending means for bending an opticalpath with a reflective surface by 90 degrees; wherein: a lens isarranged at a position most toward a reduction side and a position mosttoward a magnification side of the entire system, the reduction side istelecentric, and the image displayed by the image display element isprojected as the magnified image which is inverted 180 degrees.
 2. Aprojection optical system as defined in claim 1, wherein a lens isarranged between the two optical path bending means.
 3. A projectionoptical system as defined in claim 1, consisting of, in order from thereduction side to the magnification side: a first optical systemconstituted by a plurality of lenses that forms the image displayed bythe image display element as the intermediate image; a first opticalpath bending means for bending an optical path with a reflective surface90 degrees; and a second optical system constituted by a plurality oflenses that forms the intermediate image on the magnification sideconjugate plane; the second optical system consisting of, in order fromthe reduction side to the magnification side, a first lens group havinga positive refractive power, a second optical path bending means forbending an optical path with a reflective surface 90 degrees, and asecond lens group having a positive refractive power.
 4. A projectionoptical system as defined in claim 1, wherein the plurality of lensesand the two optical path bending means are arranged at a positionfurther away from the magnification side conjugate plane than the imagedisplay element.
 5. A projection optical system as defined in claim 1,wherein, among the plurality of lenses, a lens surface most toward themagnification side is arranged at a position further away from themagnification side conjugate plane than a lens surface most toward thereduction side.
 6. A projection optical system as defined in claim 1,wherein, among the plurality of lenses, a lens surface most toward themagnification side is an aspherical surface.
 7. A projection opticalsystem as defined in claim 1, in which Conditional Formula (1) below issatisfied:135≤2ω  (1) wherein 2ω is a full angle of view of the projection opticalsystem.
 8. A projection optical system as defined in claim 3, in whichConditional Formula (2) below is satisfied:1.50<f2/|f|<2.80   (2) wherein f2 is a focal length of the secondoptical system, and f is a focal length of the entire projection opticalsystem.
 9. A projection optical system as defined in claim 8, in whichConditional Formula (2-1) below is satisfied:1.52<f2/|f|<2.20   (2-1).
 10. A projection optical system as defined inclaim 3, in which Conditional Formula (3) below is satisfied:8.20<Imφ·f2/f2<20.00   (3) wherein Imφ is an effective image diameter atthe reduction side, f2 is a focal length of the second optical system,and f is a focal length of the entire projection optical system.
 11. Aprojection optical system as defined in claim 10, in which ConditionalFormula (3-1) below is satisfied:8.30<Imφ·f2/f2<16.00   (3-1).
 12. A projection optical system as definedin claim 3, in which Conditional Formula (4) below is satisfied:0.020<enP/TL2<0.160   (4) wherein enP is a distance along an opticalaxis from a surface most toward the magnification side in the secondoptical system to a position of an entrance pupil in the case that themagnification side is a light entry side, and TL2 is a distance alongthe optical axis from a surface most toward the reduction side in thesecond optical system to the surface most toward the magnification sidein the second optical system.
 13. A projection optical system as definedin claim 12, in which Conditional Formula (4-1) below is satisfied:0.050<enP/TL2<0.145   (4-1).
 14. A projection optical system as definedin claim 3, in which Conditional Formula (5) below is satisfied:0.125<Imφ/TL2<0.240   (5) wherein Imφ is an effective image diameter atthe reduction side, and TL2 is a distance along an optical axis from asurface most toward the reduction side in the second optical system to asurface most toward the magnification side in the second optical system.15. A projection optical system as defined in claim 14, in whichConditional Formula (5-1) below is satisfied:0.130<Imφ/TL2<0.200   (5-1).
 16. A projection optical system as definedin claim 1, in which Conditional Formula (6) below is satisfied:4.0<Bf/|f|  (6) wherein Bf is a back focus of the entire projectionoptical system and f is a focal length of the entire projection opticalsystem.
 17. A projection type display device, comprising: a lightsource; light valves into which light from the light source enters; anda projection optical system as defined in claim 1 as a projectionoptical system that projects, on a screen, an optical image formed bylight which is optically modulated by the light valves.
 18. A projectionoptical system as defined in claim 1, in which Conditional Formula (7)below is satisfied:10.0<TL1/|f|<50.0   (7) wherein TL1 is a distance along an optical axisfrom a surface most toward the reduction side in the first opticalsystem to a surface most toward the magnification side in the secondoptical system, and f is a focal length of the entire projection opticalsystem.
 19. A projection optical system as defined in claim 18, in whichConditional Formula (7-1) below is satisfied:15.0<TL1/|f|<40.0   (7-1).
 20. A projection optical system as defined inclaim 1, in which Conditional Formula (8) below is satisfied:8.0<D12/|f|<30.0   (8) wherein D12 is the distance along the opticalaxis between the first optical system and the second optical system, andf is a focal length of the entire projection optical system.
 21. Aprojection optical system as defined in claim 20, in which ConditionalFormula (8-1) below is satisfied:10.0<D12/|f|<25.0   (8-1).
 22. A projection optical system as defined inclaim 14, in which Conditional Formula (5-1a) below is satisfied:0.130<Imφ/TL2<0.240   (5-1 a).
 23. A projection optical system asdefined in claim 22, in which Conditional Formula (5-1b) below issatisfied:0.138≤Imφ/TL2<0.240   (5-1b).
 24. A projection optical system as definedin claim 16, in which Conditional Formula (6-1a) below is satisfied:5.0<Bf/|f|≤13.45   (6-1a).
 25. A projection optical system as defined inclaim 24, in which Conditional Formula (6-1b) below is satisfied:6.49≤Bf/|f|<13.45   (6-1b).